Elucidation of Ion Exchange Property of Brown Coals in Relation to Their Higher Order Structure

本项目旨在阐明澳大利亚褐煤Yallourn和Loy Yang的离子交换性质。预计这一性质将严重依赖于煤的高阶结构。取得的主要结果如下：1.研究结果。发现过渡金属阳离子的交换进行得很慢。通过预先将煤的官能团与钠或钙进行交换，发现与铁或镍离子的交换发生得很快。煤接受阳离子的能力在很大程度上受到热处理的抑制，尽管酸性官能团的数量并没有减少那么多。在交换溶液中加入丙酮、甲醇或乙醇等有机溶剂，可以显著提高热处理煤的阳离子交换程度，而且这种效果似乎与煤的膨胀程度有关。阳离子交换速率随阳离子种类和温度的不同而不同。乙醇的加入没有改变阳离子交换的速率，但改变了阳离子交换的程度。碱提腐植酸的量随热处理温度的升高而降低，但与钙的交换保持了热处理煤中腐植酸的易萃取性。溶胀实验表明，热处理降低了溶胀度。交换钙似乎能抑制肿胀。钴和镍混合溶液中阳离子交换的选择性不表现出对特定阳离子的任何偏好。钴-镁溶液的选择性与溶液的pH值有一定关系。这种行为可以根据水合阳离子的半径来解释。

The present project aims at elucidating the ion exchange property of Australian brown coals, Yallourn and Loy Yang. The property is expected to be heavily dependent of the higher order structure of the coals. The main results obtained are as follows.1. Exchange of transition metal cations is found to proceed only slowly. By pre-exchanging the functional groups of coal with sodium or calcium, the exchange with iron or nickel cations were found to take place rapidly.2. The ability of coals to accept cations is largely suppressed by heat treatment, though the number of the acidic functional groups did not decrease so much. By adding to the exchange solution organic solvents such as acetone, methanol or ethanol, the extents of cation exchange of heat-treated coals were found to be promoted profoundly and the effects seem to correlate with the swelling of the coal.3. The rate of cation exchange is found to vary depending on the cation species and the temperature. The addition of ethanol did not change the rate, but the extent of cation exchange.4. The amount of extracted humic acid by alkali decreased with the temperature of heat treatment, but the exchange with calcium maintained the easiness for extraction from heat treated coals.5. Swelling experiments indicated a reduction in the degree of swelling due to heat-treatment. Exchanged calcium seems to suppress the swelling.6. Selectivity of cation exchange from mixed solutions of cobalt and nickel did not show any preference to a particular cation. Some dependence on pH of the solution was noted for the selectivity from cobalt-magnesium solution. The behavior can be explained on a basis of the radius of the hydrated cations.